Currently, a communication device, such as mobile phone, having a metal housing, has becomes a mainstream structure of the mobile phones of various brands. When designing an antenna of the mobile phones, a slit is usually defined in the metal housing. Generally, by the slit through the housing along a width direction of the mobile phone, the housing is divided to form a three-piece structure including a top frame portion, a middle portion and a bottom frame portion, and then the slit is filled with a plastic member. Apparently, the slit area of such all-metal housing is relatively great, which influences a structural strength and a visual quality of the whole metal housing.